SHAFAQNA – According to all known rules of modern politics,Conservative ministers and MPs should have been returning from Birmingham last night hollow-eyed and broken. Their party conference should have been a complete, unmitigated disaster after Sunday’s newspapers brought news of a so-called “double hammer blow”, a baleful combination of one ministerial sex scandal and the defection to Ukip of an MP.

Nor was that all. The party remains beset by arguments about Europe. With eight months to a general election, it lags Labour badly in the polls. Every one of the ingredients was in place for the customary outbreak of mayhem, back-biting and blind panic.

This did not happen. No leadership threat materialised. Cabinet ministers delivered a series of confident, intelligent, agenda-setting speeches. There were more party members in evidence than in previous years. They outnumbered commercial lobbyists, which was especially welcome. Overall this was one of the most harmonious, good-natured and creative Tory conferences I have ever attended. The party suddenly looks and feels at ease with itself – something I haven’t experienced in more than 20 years of reporting politics.

The good order and sense of purpose at Birmingham was all the more striking in comparison with events elsewhere. Ukip may have had a glorious location – Doncaster racecourse – but in policy terms their conference was a shambles. Even Labour’s supporters acknowledge that theirs didn’t seem like a party preparing for government at Manchester. The Conservatives, in sharp contrast, have a plan for power and a record of achievement in domestic policy they can be proud of. Indeed, the conference was so rich in announcements that the most important went unnoticed.

Iain Duncan Smith’s disclosure that the teething problems have been resolved and that the Universal Credits system will be rolled out across the country ahead of the election was momentous. Many critics, not just on the Left, cheerfully predicted that Mr Duncan Smith’s welfare reforms would fail. They are now irreversible, and as a result Mr Cameron’s Coalition will be able to claim a place among Britain’s great reforming governments.

Nevertheless, the Prime Minister faced enormous challenges when he arrived to deliver his speech yesterday. He has encountered severe criticism, especially from his supporters, for appearing detached and indifferent to the concerns of ordinary people. These criticisms have been borne out in opinion polls, which consistently show that voters consider Ed Miliband to have a better understanding of their worries.

Others have started to wonder what David Cameron is for, maintaining that he is an essentially meaningless figure who is using the party for his own nefarious purposes. There is a certain kind of Right-wing Tory who is convinced that Mr Cameron believes in nothing at all, and will make any number of compromises to cling on to office. They dislike his motives and distrust his personal connections.

Behind all this irascibility lurks a much deeper problem. Mr Cameron has been leading what is still a party of government into the shapeless, modern age of political insurgency. He is a traditional politician, in the school of Harold Macmillan, trying to govern at a time when the political class is facing a potentially fatal crisis of legitimacy. Hence the rise of the SNP in Scotland and Ukip in England.

This remarkable juxtaposition meant that in Birmingham David Cameron was not just trying to redeem his own career. Nor was he simply trying to rescue the electoral fortunes of his party. Above all, the Prime Minister was fighting to show how the political structures that have governed Britain for the past century are still relevant in 2014. He was battling to make the case that traditional politics can offer solutions to British problems in a way that the insurgents cannot.

In my cautious judgment, he succeeded. He delivered his finest and most important conference address since the autumn of 2007 when, by force of political oratory, he frightened Gordon Brown out of holding a general election. That speech saved Cameron’s leadership, his party and, arguably, the nation. Yesterday’s gave the Conservatives a fighting chance of winning the election.

While he was at it, Mr Cameron dealt effectively with the crude and insulting proposition, much favoured at Labour’s conference, that he is in politics to further enrich a small group of already privileged friends and dependants, while destroying the life chances of everyone else. He made a strong case that his Government is not like that. It has its faults. But it is at bottom a noble project: ancient Conservative ideas about the inherent nobility of human nature, rather than the socialist reliance on the power of the state, lie at the heart of his schemes to rescue Britain’s health, education and welfare systems.

Unlike Ed Miliband, he did not forget about the deficit. He made the simple, powerful and truthful point that no country can have decent public services without a dynamic economy. Cuts are not, as Labour maintains, part of a demented Right-wing plan to destroy public services. They are vital if public services are to survive at all. Mr Cameron spelt this out with logic, skill and passion. His speech was a masterclass.

Britain is about to embark on a very curious but rather frightening constitutional experiment. Little or no serious business will get done when Parliament reassembles next week. Formally the Coalition may continue, but in practice not. December’s Autumn Statement is likely to be the Coalition’s last meaningful act. Parliament will become pointless, Cabinet a waste of time. Next year’s Budget will be a joke. In a normal political cycle, Mr Cameron would have used his splendid conference speech as an election launch pad. That is impossible now, though, because of the Fixed-Term Parliaments Act agreed between the two Coalition parties after the 2010 election. As a result, Britain can look forward to a period of political inertia of the type usually associated with countries such as Belgium or Italy. This paralysis could easily continue after the May election: if current trends continue, it is easy to imagine a result that creates a multi-party coalition rendering Britain ungovernable in the conventional sense of the word.

It would be helpful for Mr Cameron to set his mind to averting this calamity. The Prime Minister has an unfortunate habit of rising to the big occasion, then making the mistake of thinking that the job has been done. He must use the looming eight months of proxy war to go out and spread the powerful message that he articulated with such verve and skill in Birmingham.

There were only a few thousand of us in the hall yesterday. He now needs to spell out his message to the nation. A vote for Farage is a vote for Miliband. A vote for Miliband is a vote for a return to the economic disaster of the Brown years. Only his party has a coherent plan for Britain.

It is impossible to say whether the Conservatives can overcome ferocious odds to win the general election. However, it can now be asserted with great confidence that they deserve to do so. Yesterday Mr Cameron made the moral, intellectual and patriotic case for voting Conservative. Now he must go out and sell it to the British people.